The present invention concerns spring-assisted movement of hinged elongated objects, particularly objects having great weight hinged at a lower end about a generally horizontal axis, and which extend upwardly therefrom to swing through an overcenter position. In particular, the present invention has applicability to assisting the opening and closing of truck hoods which may weigh from 200 lbs. to 400 lbs. or more. Typically, such truck hoods are opened by swinging forward pivotal movement about a hinge located adjacent to the front bumper, the truck hood (and in some cases a portion of the cab) being progressively tilted forward until the truck engine is fully accessible.
Various attempts have been made to control the movement of truck hoods including the use of springs, levers, hydraulic assists, cables, counterbalances and the like, without satisfactorily balancing and minimizing opening and closing forces while maintaining safety. Due to the great weight which large truck hoods generally have, opening or closing such hoods can be extremely hazardous if the mechanism which controls the hood should fail, causing serious injury and even death. Examples of prior devices of the type mentioned may be found in U.S. Pat. Nos. 3,157,240; 3,419,099; 3,754,613; 3,765,500 and 4,090,579.
It is the purpose of the present invention to disclose a simple yet effective and safe mechanism for controlling the swinging movement of elongated hinged bodies, for example, truck hoods and tailgates having great weight, which greatly minimizes the force necessary to initiate opening or closing of the truck hood and provides a steady force to assist continuous hinged movement of the truck hood between an opened and closed position.